A toy inventor's marble run design has a problem—the marble gets stuck before reaching the finish! Students step in as toy engineers to solve this movement challenge by exploring forces, energy, motion, and speed. They investigate how ramps, gravity, and friction affect marble movement, then collaborate to design and build their own marble run prototypes using everyday materials. Students apply the engineering design process to test and improve their designs, experimenting with different track features to keep marbles rolling. The unit culminates with teams presenting their marble runs and reflecting on the engineering principles that guided their solutions.